Abstract

The Rydberg and valence transitions of , , and are studied using laser-based 1 extreme ultraviolet UV two-photon-ionization spectroscopy, supplemented by synchrotron-based photoabsorption measurements in the case of . For each isotopomer, effective rotational interactions between the and levels are found to cause strong -doubling in and dramatic -branch intensity anomalies in the band due to the effects of quantum interference. Local perturbations in energy and predissociation line width for the Rydberg level are observed and attributed to a spin-orbit interaction with the crossing, short-lived valence level.